Emily A. A. Jarvis

Imaging the interface of epitaxial graphene with silicon carbide via scanning tunneling microscopy

Graphene grown epitaxially on SiC has been proposed as a material for carbon-based electronics. Understanding the interface between graphene and the SiC substrate will be important for future applications. We report the ability to image the interface structure beneath single-layer graphene using scanning tunneling microscopy. Such imaging is possible because the graphene appears transparent at energies of

Effects of Oxidation on the Nanoscale Mechanisms of Crack Formation in Aluminum

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Coordination Studies of Al-EDTA in Aqueous Solution

above or below the Fermi energy

The role of reactive elements in thermal barrier coatings

({E}_{F})

Weak bonding of alumina coatings on Ni(1 1 1)

. Our analysis of calculations based on density-functional theory shows how this transparency arises from the electronic structure of a graphene layer on a SiC substrate.

Metallic Character of the Al2O3(0001)-(x31 x31)R ( 9° Surface Reconstruction †

Materials failure, in the form of cracking, is a phenomenon of fundamental scientific interest and one that impacts a variety of applications spanning a wide range of fields, particularly those of materials science and engineering. Experiments have investigated extensively the macroscopic properties associated with cracking within homogeneous materials as well as at interfaces between dissimilar materials. Likewise, theoretical modeling via engineering finite-element approaches and molecular dynamics simulations with empirical embedded-atom potentials 3] have provided some insight into cracking mechanisms. Nevertheless, these models rely on inherent assumptions concerning interatomic and/or bulk behavior, a drawback in instances where fundamental atomic interactions are poorly understood or improperly characterized by overly simplified model potentials. A comprehensive study incorporating a first principles approach at the atomic scale and effectively linking this information to the macroscopic scale poses an array of challenges, implementational and otherwise. To date, these difficulties and the computational expense associated with first principles calculations have generally motivated employing empirical assumptions to treat mechanics of the smallest length-scale regime. Resorting to empirical models limits the chemistry that may be accounted for. Accordingly, despite widespread scientific interest in the cracking phenomenon, aspects of the microscopic failure mechanisms remain largely a mystery. Herein, we investigate some aspects of the atomic-level properties which lead to chemically induced crack formation within a simple model. Finding methods to smoothly and effectively couple microscopic to macroscopic modeling is an active area of research 5] and will provide much-needed insight into a complete mechanism for chemically induced cracking. Aluminum is an important engineering material used in a variety of applications; to understand its behavior under stress is essential. Under ambient conditions, a self-limiting oxide layer forms on the aluminum surface and protects the underlying metal from further oxidation. This, in addition to their light [12] J. Hofkens, M. Maus, T. Gensch, T. Vosch, M. Cotlet, F. Köhn, A. Herrmann, K. Müllen, F. C. De Schryver, J. Am. Chem. Soc. 2000, 122, 9278. [13] J. Hofkens, L. Latterini, G. De Belder, T. Gensch, M. Maus, T. Vosch, Y. Karni, G. Schweitzer, F. C. De Schryver, A. Herrmann, K. Mullen, Chem. Phys. Lett. 1999, 304, 1. [14] Y. Karni, S. Jordens, G. De Belder, G. Schweitzer, J. Hofkens, T. Gensch, M. Maus, F. C. De Schryver, A. Herrmann, K. Mullen, Chem. Phys. 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Exploiting Covalency to Enhance Metal-Oxide and Oxide-Oxide Adhesion at Heterogeneous Interfaces

The degree of aluminum toxicity is based on its complexation with organic ligands. One of these complexes is AlEDTA- (Al = aluminum, EDTA = ethylenediaminetetraacetate), the structure of which in aqueous solution has been debated on the basis of X-ray absorption and NMR measurements with different interpretations proposing different coordination. In addition, there is a lack of consensus regarding the relationship of crystalline AlEDTA- and its geometry in solution. This debate must be resolved, not merely for scientific interest, but because the use of an incorrect coordination might lead to the wrong interpretation of bioactivity and kinetics data. In this work, we predict the coordination of Al in aqueous AlEDTA- by employing ab initio calculations and Car-Parrinello molecular dynamics simulations. Our results indicate that AlEDTA- favors Al in octahedral coordination in aqueous solution. Furthermore, the predicted crystalline and solution-phase structures of AlEDTA- are similar and agree well with recent X-ray measurements, supporting the strong chelating nature of this metal-organic complex in aqueous solution.

An Atomic Perspective of a Doped Metal-Oxide Interface †,‡

With the assistance of high-performance computing, the authors employ density functional theory (DFT) calculations to investigate atomic-level interactions at interfaces between ceramics and metals. They present their findings, based on DFT calculations, characterizing ideal interfaces related to those present in typical thermal barrier coatings.